Nidhogg

Get eaten by the nidhogg after nearly allowing your opponent to do the same

Trap your opponent on your sword for a long time

Beat the singleplayer game

Win the faceoff and never lose the arrow in a singleplayer match

100 total kills in one match

Run across your final screen in the castle with your sword cocked the whole time

Finish an 8 player tournament

Let the timer run out in your opponent's last screen and win in sudden death

Play a match lasting longer than 20 minutes

Dominate every level in one singleplayer game